Method for lapping gears

ABSTRACT

A new method and machine for lapping hypoid gear pairs to provide improved tooth engagement characteristics, resulting in good sound qualities over a remarkably increased range of pinion axial adjustment in assembly. The method employs a plurality of lapping cycles to achieve full control of tooth surface mismatch. The lapping machine controls backlash settings, set-overs, and all lapping motions with only three actuators, carries out the new method and achieves a versatility of lapping control far exceeding that available in prior art machines. A control panel provides an array of thumbwheel switches, graduated dials and selector switches for rapid entry of all lapping cycle control data, i.e., backlash, lapping motions and motion rates, number of passes, speeds and torques, all of these parameters being controlled independently for both forward and reverse sides of the teeth. The control panel also permits ready selection of alternative lapping methods including conventional one-cycle lapping methods as well as the novel multi-cycle methods disclosed herein. Stepping motors, responsive to data entered into the control panel, operate linear actuators to displace the gear spindle for effecting all lapping motions and relative gearto-pinion displacements. The machine also is designed with a vertically oriented pinion spindle to reduce floor space and to facilitate adaptation to full automation.

United States Patent 1 Spear [in 3,712,000 [451' Jan. 23, 1973 METHOD FOR LAPPING GEARS [75] Inventor: Gilmore M. Spear, Rochester, NY.

[73] Assignee: The Gleason Works, Rochester,

221 Filed: Dec. 16, 1970 211 App]. No.: 98,510

[52] US. Cl. ..5l/287, 29/90 B, 51/26, 73/162 [51] Int. Cl. ..B24b H00 [58] Field of Search ..5 H26, 287', 29/90 B; 73/162 [56] References Cited UNITED STATES PATENTS 1,796,484 3/1931 Slade ..5l/26 X 2,904,934 9/1959 Schicht ..51/26 2,919,518 1/1960 Bauer et a1. ..5l/26 2,947,120 8/1960 Bauer et a1. v ..5 H26 2,961,873 11/1960 Carlsen ..51/26 X 2,984,956 5/1961 Schicht ..5 H287 3,069,813 12/1962 Bauer et a1. ..5 l/26 3,099,901 8/1963 Hunkeler ..5l/287 X Primary ExaminerDonald G. Kelly Attorney-Morton A. Polster [57] ABSTRACT A new method and machine for lapping hypoid gear pairs to provide improved tooth engagement c liaracteristics, resulting in good sound qualities over a remarkably increased range of pinion axial adjustment in assembly. The method employs a plurality of lapping cycles to achieve full control of tooth surface mismatch. The lapping machine controls backlash settings, set-overs, and all lapping motions with only three actuators, carries out the new method and achieves a versatility of lapping. control far exceeding that available in prior art machines. A control panel provides an array of thumbwheel switches, graduated dials and selector switches for rapid entry of all lapping cycle control data, i.e., backlash, lapping motions and motion rates, number of passes, speeds and torques, all of these parameters being controlled independently for both forward and reverse sides of the teeth. The control panel also permits ready selection of alternative lapping methods including conventional one-cycle lapping methods as well as the novel multicycle methods disclosed herein. Stepping motors, responsive to data entered into the control panel, operate linear actuators to displace the gear spindle for effecting all lapping motions and relative gear-topinion displacements. The machine also is designed with a vertically oriented pinion spindle to reduce floor space and to facilitate adaptation to full automation.

8 Claims, 9 Drawing Figures PATENTEDJANZB I975 3.712.000

SHEET 1 0F 8 FIG. I

GIL HOPE M- SPEAR INVENTOR.

PATENTEU JAN 23 I975 SHEET 2 BF 8 SHEET 4 BF 8 n3. Spy v rlfllh r ar IIM Q III . F 5: 2+ 2 &

PATENTEDJAN 23 1975 METHOD FOR LAPPING GEARS BACKGROUND OF THE INVENTION Spiral bevel and hypoid gears are usually lapped after they have been cut and heat treated, to refine the tooth surfaces and to improve tooth contact. Lapping includes running together a gear pair, i.e., a spiral bevel or hypoid gear and a corresponding pinion, under moderate loads while a lapping compound is sprayed on the gears. Once two gears have been lapped together, they are maintained as a pair.

In the course of adapting gears to fit particular applications, the tooth surfaces are shaped so that the gears can tolerate a specified combination of displacements without causing the contact to move off the tooth surface. In order to accomplish this, most spiral bevel and hypoid gears are carefully developed in the cutting to have combined mismatch; i.e., they are relieved in both the profile and lengthwise directions so that only a local area generally at or close to the center of the tooth is unchanged from the theoretically conjugate surface. In lapping such gears, it is desirable to maintain control of mismatch, and problems have been commonly encountered in the past due to lack of adequate control, and particularly clue to the tendency of lapping to reduce profile mismatch in hypoids. Properly localized tooth contact allows for displacement of the contact under loads, e.g. because of housing and bearing deflections, and for slight errors in positioning of gears in assembly, without causing concentration of the load at the ends of the teeth or affecting the running qualities, e.g. quietness, of the gears when operating. The inadequate control of mismatch has resulted in gear sets which are extremely sensitive to small positioning errors in the assembly with attendant objectionable sound characteristics.

During the lapping operation, the relative position of the gear and pinion is varied by combinations of three motions so that the entire working area of the teeth may be lapped. The three lapping motions are l) axial movement of the gear relative to the longitudinal axis of the gear, (2) axial movement of the pinion relative to the longitudinal axis of the pinion, and (3) lateral movement of the pinion axis relative to the gear in a sense to change the hypoid offset. (Because the motions are relative, they may be accomplished by moving either the gear or the pinion or both.) For purposes of this disclosure, these three motions will be designated G, P, and E, respectively.

Typically,.the E, P and G movements each have an effect on both the lengthwise and depthwise position of the localized tooth contact pattern, the primary effect of E movement being on the relative lengthwise position of the contact pattern, the primary effect of P movement being on the relative depthwise position of the contact pattern, and the primary effect of G movement being on the backlash. Generally, in lapping, it is desirable to traverse the contact pattern lengthwise of the tooth: center to toe, return to center, center to heel, and return to center, while maintaining constant backlash and such traversing can be effected in such a manner as to provide lapping of the entire surfaces of the drive and coast sides of the teeth.

The ratios of E, P and G movements needed to provide the desired lengthwise traverse and constant backlash from center to heel (and vice versa) and center to toe (and vice versa) are not quite the same, nor are these ratios necessarily the same for the drive and coast sides of the teeth. Most early lapping machines did not take the foregoing into account, but other lapping machines of modern vintage have such a capability. Examples of such machines may be seen from Bauer et al. U.S. Pat. No. 2,947,120, issued Aug. 20, 1960 and No. 3,069,813, issued Dec. 29, 1962 and Hunkeler US. Pat. No. 3,099,901, issued Aug. 6, 1963.

It should be apparent that machinery for providing basic lapping motion control must be fairly complex, even before one begins to consider the design complexities required to provide additional machine capabilities often considered desirable, e.g., ability to make additional traverses at different depths, to vary traverse rates at different points, and to vary the location of the mean point (where the traverse begins) for the drive side and the coast side. To the extent that prior machines lack capability of adjusting any of the factors which have been discussed or lack the capability of adjusting and controlling certain of these factors independently of others and automatically, they fail to provide a versatility desired by industry.

The need for more versatile machines, capable of fast and efficient operation, and susceptible for use in highly automated manufacturing facilities has inspired the subject innovation in the structure and control of gear lappers.

In addition to satisfying this long-standing need for greater versatility, the invention herein provides a novel machine orientation having important advantages over prior lapping machines which mount both the gear and the pinion on horizontal axes at the lapping station. The novel lapper orientation disclosed herein mounts the gear on a horizontal axis and the pinion on a vertical axis, and this new machine configuration is superior to the prior art orientation, for installations, for reasons which will be outlined below.

Another industry need to which the subject invention relates is the lapping of gears requiring a particularly fine finish. After a gear pair has been rough lapped, it is sometimes desirable to additionally refine the tooth surface finish without significantly changing the tooth bearing shape and position as accomplished in the rough lap. As different from prior art machines which,-

if such a further feather lap is desired, requires the operator to make a separate machine set up, the novel machine disclosed herein permits such additional fine lapping to be selected and carried out automatically as a regular part of the lapping routine.

The invention herein also provides a marked improvement in gear adjustability and noise characteristics, a major problem area in the gear manufacturing industry. A principal concern in lapping is the control of bearing position on the tooth, and in the most commonly employed prior art lapping method, this frequently results in the excess lapping of a particular area of the tooth. This excessive lapping in turn causes excessive profile width (i.e., a loss in depthwise curvature of the tooth face), resulting in increased sensitivity rough lapping to control bearing position while maintaining, and even remarkably improving, the adjustability and sound qualities of a gear pair.

Those skilled in the art will be aware that the same novel design disclosed herein in relation to a machine used for lapping gear pairs, may be used for machines for testing gear pairs which have been lapped previously. Of course, such testing machines would not require means for handling and applying lapping compound, nor means for providing certain lapping motions which are not required for testing.

SUMMARY OF THE INVENTION The novel lapper disclosed herein is provided with one vertical spindle and one horizontal spindle (instead of two conventionally horizontal spindles). The two spindles are oriented with respect to the front of the machine in such a way as to facilitate automatic loading, namely, to permit the use of loading devices which can move transversely of the front of the machine to remove the lapped gear pair and to mount the gear pair which is to be lapped. Also, with such spindle orientation the machine may be more rigidly constructed: since the offset adjustment is not vertical, the spindle housings may be more closely coupled to the frame, and the housing, which adjusts for offset, may be fully supported. in addition, the machine can be smaller, in plan view, for a gear member of a given size, taking up less valuable floor space. The distance from the centerline of the vertical spindle to the front of the machine is less than it would be if the gear rather than the pinion were to be mounted thereon, so the machine operator is closer to the work, and the machine may be more easily served. This facilitates making adjustments and handling and observing the work.

It is known in the manufacture of spiral bevel and hypoid gears that by properly controlling tooth surface mismatch in the profile (depthwise) direction, as well as in the lengthwise direction, a control may be achieved over the direction of the path on the tooth surface of the instantaneous points of contact. The invention herein is based upon the discovery that by a novel application of these known controls, automotive type hypoid gears may be manufactured which combine quiet operation with remarkably increased pinion axial adjustability, and it has been demonstrated experimentally that the novel lapping method disclosed herein, which comprises a predetermined combination of several different lapping cycles, will produce gears having such remarkably improved characteristics.

Further, as noted above, known lapping machines have lacked versatility in their provisions for economically effecting desired controls over basic lapping operations.

The novel lapping machine disclosed herein provides means for selectively controlling and combining at least three different cycles of lapping operation in a fully automated process.

The three basic cycles comprise (l a semi-finishing cycle (i.e., conventional lapping) in which the contact pattern is traversed toe and heel in the generally known manner for a selected number of passes to obtain desired bearing position and desired lengthwise mismatch, (2) a first tip lapping cycle in which the bearing location is displaced high on the tooth of one member by means of a relative positive set-over of the pair, followed by a heel and toe lapping traverse of the tip periphery for a selected number of cycles and (3) a further tip" lapping cycle in which the bearing location is displaced high on the tooth of the other member by means of a relative position setover of the pair, followed by a heel and toe lapping traverse of the tip periphery for a selected number of cycles.

The described lapping method is carried out with independently controllable set-overs, lapping motions, lapping speeds, torques, and traverse rates for the semifinish cycle and for the tip lap cycles, and all three basic lapping cycles are each independently controllable for forward and reverse sides of the teeth.

In addition to the novel three-cycle lapping method described above, the subject apparatus permits the selection of other basic lapping cycle combinations, e.g., (1) conventional semi-finish lapping, as described above as the first cycle of the three-cycle method, or (2) a two-cycle lapping method which consists of a conventional semi-finish cycle followed by a second feather lapping cycle of shorter traverse, intended to refine the finish in the central and most used areaof the tooth without significant effect on bearing shape and position.

in order to accomplish this versatile automatic operation three different groups of set-over displacements (for run, drive and coast) and three lapping motions (G, P and E) are provided by moving sub-assemblies about three respective axes. By preference, the sub-assemblies are automatically moved by program-controlled stepping motors.

The preferred embodiment of apparatus for practicing the invention herein provides all the following capabilities: different mean points, drive and coast; different E/P ratios, drive and coast; different distance traveled, drive and coast; different distances traveled to toe versus heel, drive and coast; different rates of travel, drive and coast; variation in traverse rate at a preselected point in traverse between heel and toe; and automatic backlash setting and control. All of these features are independently selectable, and different variables including time, distance, and the sequence and type of lapping cycles may be chosen independently for the drive and coast sides of the gear pair, on the same machine with fully automatic operation requiring no manual manipulation or attention to the machine or the gear pair.

it will be appreciated by those skilled in the art that the versatile operation just described generally above requires a great number of setovers of the relative orientation of the spindles to establish backlash and different mean positions of tooth bearing for the gear pair being lapped as well as progressions of relative spindle movements for causing the tooth bearing to be traversed along various mean-to-heel and mean-to-toe paths from the variously established mean position. The machine disclosed herein greatly simplifies the mechanics of these complex motions by producing all of these relative spindle movementsfor backlash, setovers, and lapping motions, with only three linear actuators (one for each respective P, G, and E line of motion), each having a respective ball screw unit driven by an independently controlled step motor, in combination with a novel gear head assembly of unusual simplicity. Even for purposes of loading the machine, only the gear head assembly moves, the pinion spindle being fixed to the machine frame, thereby providing exceptional rigidity and minimizing alignment problems prevalent in prior art machines in which both spindles are mounted on movable slides.

The principles of the invention will be further hereinafter discussed with reference to the drawings wherein preferred embodiments are shown. The specifics illustrated in the drawings are intended to exemplify, rather than limit, aspects of the invention as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings FIG. 1 is an isometric view ofa lapper embodying the principles of the present invention, showing the relative positions of the gear and pinion spindles, the gear head structure with its three axis adjustment means and, generally depicted, the automatic control means for the lapper;

FIG. 2 is a fragmentary side elevation view of the lapper, showing the gear head structure, vertical adjustment means, cross slide and the three stepping motorlinear actuator mechanisms;

FIG. 3 is a longitudinal vertical sectional view of one linear actuator mechanism taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a vertical transverse sectional view of one linear actuator mechanism, taken substantially along line 44 of FIG. 3, showing the zero lock" trip dogs, pistons and switches;

FIG. 5 is a fragmentary transverse vertical sectional view of the lapper, taken substantially along line 55 of FIGS. 2 and 6, showing the interior of the gear head structure including the pivot bracket, linear actuator mechanism, gear spindle, gear spindle housing and ball swivels;

FIG. 6 is a horizontal sectional view of the gear head structure taken substantially along line 6-6 of FIG. 5;

FIG. 7 is a simplified block electrical diagram of the lapping motion controller;

FIG. 8 is a schematic example of one-half of the lapping motion controller control panel set for carrying GEAR HEAD ASSEMBLY AND THREE ACTUATOR UNITS In FIG. 1 there is shown a gear lapper 10 and an electronic control unit 12 which is electrically connected to the gear lapper to receive responses from parts of the lapper and send commands to it.

The machine 10 includes a frame 14 having, at its front, a lapping chamber (work station) 16 into which there projects a vertically, upwardly extending pinion spindle l8 and a horizontally, forwardly extending gear spindle 20. The lapping chamber 16 is shown disposed at a height to be conveniently served by a human operator. At the left side of the front of the machine, below the lapping chamber are shown disposed the housing 22 for an eddy-current drive system having a constant speed motor 24 electromagnetically coupled to an output shaft. Motor 24 drives the pinion spindle 18 through a belt 26 at speeds selected by well-known current control devices (not depicted) which vary the field strength of the electromagnetic coupling. In the corresponding position at the right side of the machine is the housing 28 for a cycle drum 30, e.g., a stack of cams keyed on a common shaft to effect a time-based control of certain sequential operations of the machine in a manner well known in the art.

The gear spindle 20 is powered for rotation by a hydraulic motor 32 driving through a belt 34. During normal lapping operations, a gear pair is mounted on the spindles, the sliding door 36 covers the lapping chamber, the teeth of the pinion and gear are in mesh, the eddy-current motor 24 drives the pinion through the belt 26 and spindle 18, the pinion drives the gear, and the hydraulic motor 32 is driven by the belt drive 34 from the gear spindle 20 and functions as a brake. The braking torque provided by the hydraulic motor 32 is adjustable in a conventional manner by varying the restriction of the motor's fluid exhaust line valving.

Looking also at FIG. 2, behind the lapping chamber, the upper surface 38 of the frame 14 has a plurality of longitudinally spaced, horizontally and transversely extending slideways 40, which mount a horizontal cross slide 42 having downwardly directed, transversely extending runners 44 that cooperate with complementarily shaped grooves 46 in the slideways 40 to permit only lateral movement of the cross slide 42 with respect to the stationary frame 14.

On its upper surface, the cross slide 42 has a plurality of transversely spaced, longitudinally extending and upwardly opening grooves 48.

A gear head structure 50 is mounted on the cross slide 42 with clamps 52 (hydraulic details omitted) engaging in the grooves 48. When the clamps 52 are engaged, the gear head structure is longitudinally fixed on the cross slide 42; when the clamps are disengaged, they permit only longitudinal sliding of the gear head structure with respect to the frame 14 on the cross slide 42. Longitudinal motion in advancing and withdrawing is provided by a fluid pressure operated means, schematically simplified as piston and cylinder arrangement 51, secured between the slide 42 and the gear head structure 50.

The gear head structure 50 has a frame 53 including vertically extending, longitudinally spaced rails 54. A vertical adjusting slide 56 is mounted on rails 54 for only vertical sliding with respect to the gear head structure. A plurality of adjustable clamps 58 are provided for fixing the vertical adjusting slide 56 to frame 53.

The gear head spindle is mounted in the gear head structure 50, and therefore lateral movement of the cross slide 42 with respect to the slideways 40 can be used to adjust the machine for running together gear pairs of differing offset. Since a single machine will generally be used with gear pairs of one nominal offset value for long periods of time, clamping means which clamp the cross slide with respect to the slideways 40 may be manually operated.

Similarly, longitudinal movement of the gear head structure 50 on the cross slide 42 is used to engage and disengage the gear pair being lapped, gear head structure 50 being withdrawn (to the rear in FIG. 1 and to the right in FIG. 2) to facilitate loading and unloading of the machine.

In loading, the gear mounted on the gear spindle is pushed axially forward, by movement of the gear head structure 50, until its teeth bottom" in meshing engagement with teeth of the pinion mounted on the pinion spindle, then the clamps 52 are engaged to lock the gear head structure with respect to the cross slide 42. To accommodate different sizes of gears, the vertical adjusting slide 56 is adjusted relative to frame 53 of the gear head structure by rotating a vernier dial 60 which turns an adjusting screw 62 journaled in the frame 53 for rotation about a vertical axis and having a threaded lower end threadably received in an upwardly opening socket 64 on the inside of the vertical adjusting slide 56. As aforementioned, the clamps 58 hold the slide 56 in its adjusted position.

In the presently most preferred embodiment, three stepping-motor driven linear actuator units 66 are mounted on the vertical adjusting slide to provide the three desired lapping displacements (E, P, and G). As seen from the right side of the machine, the three units 66 are disposed in an L-shaped configuration with the units for effecting E movements at the upper left of the vertical adjusting slide 56, the unit for effecting P movements at the lower left of the slide, and the unit for effecting G movements at the lower right of the slide.

Each of the actuator units 66 (which are shown in most detail in FIGS. 3-5 and are also depicted in whole or in part in FIGS. 1, 2 and 6) includes a rotary stepping motor 68 mounted on a housing 70 for a linear actuator 72. Each motor 68 is responsive to pulses from the electronic control unit 12 and imparts rotation to a worm 74 which is in mesh with a worm wheel 76 which is, in turn, keyed to a sleeve 78. The sleeve is journaled for rotation by bearings 80 in the housing 70. The sleeve 78 receives in its bore a ball-nut unit comprising a nut 82 threadably engaged to a linear screw 84 by ball threads 86 in a well-known manner.

One end of the linear screw 84 is of non-circular cross section 88 and is axially slidable in a complementarily cross-sectioned socket 90 secured in the end cap 92 of the housing 70 asa rotation restraint for the linear screw. Thus, as the sleeve 78 and the nut 82 secured to it are caused to rotate, the linear screw 84 is moved axially a very small amount (e.g., 0.0I inch).

With particular reference to FIGS. and 6, it will now be explained how axial movements of linear screws 84 of the G, P and E linear actuator units 66 produce the desired G, P and E movements necessary to the lapping of a gear pair mounted on the spindles 18, 20.

Two of the lapping motions (E and P) can be understood from reference to FIGS. 5 and 6. The gear spindle is mounted in a housing 1 12 rigidly attached to pivot shaft 122 which is rotatably mounted and constrained against axial movement in pivot bracket 120. Pivot shaft 122 is horizontal, parallel to, and in substantially the same vertical plane as the gear spindle 20. A projecting ear 114 of housing 112 is further operably connected to the pivot bracket 120 by means of a pin 116 and spring 118. The spring urges the housing 112 clockwise in FIG. 5 about the axis of shaft 122.

Each linear screw 84, for the respective E and P units 66, carries a plunger 124 which has a socket at its inner end. Opposite each plunger 124 is a bearing 126 affixed, respectively, to the housing 112 and the pivot bracket 120. Each bearing 126 provides a pressure sur-- face for a respective swivel cup 128 which is freely slidable thereon. Each cup 128 has a spherical seating surface disposed toward a co-acting spherical seating surface of the plunger 124. The cup and plunger receive a bearing ball 130 therebetween.

In the interconnection of the pivot bracket 120, the gear housing 112 and the E motion actuator elements, the spring 118 acts to urge the housing clockwise about the axis of pivot shaft 122 and holds E motion actuator elements 84, 124, 126, I28, and 130 in firm engagement. By virtue of the mounting structure just described, it can be seen that the housing 112 moves angularly about pivot 122 in response to axial movement of the linear actuator screw 84 of the E motion unit. The distance between the pivot shaft 122 and the spindle 20 is sufficiently great, when compared to the small degree of angular motion of the housing 112 produced by the slight extension and retraction of the linear actuator screw of the E motion unit, that the resulting displacement of the gear spindle can be considered as being a substantially linear motion in the direction of the arrow E-E drawn on the longitudinal axis of the gear spindle in FIG. 5.

The P motion, indicated by the arrow P-P of FIG. 5, is similarly provided by pivoting of the pivot bracket about the horizontal pivot shaft 132 which is parallel to the gear spindle and in the substantially same horizontal plane with it. The small angular displacements of the gear spindle 20 produced by slight axial extension and retraction of the linear actuator screw 84 of the P motion unit 66 can be considered to be substantially linear movements in the direction of the arrow P-P.

The pivot bracket 120 is secured on the pivot shaft 132 via a yoke arrangement 134 including two longitudinally spaced radially projecting ears disposed at opposite side edges of the vertical adjusting slide 56. In the interconnection of the pivot bracket 120, slide 56, and the P motion actuator elements, the weight of the bracket 120, housing 112, and spindle 20 act to urge the entire bracket, housing and spindle assembly counterclockwise about the axis of shaft 132, and holds P motion actuator elements 84, 124, 126, 128 and in firm engagement. Plate 136 and springs 138 provide biasing means to relieve the P motion linear actuating unit of a portion of the gravity load of the bracket, housing and spindle assembly.

In the preferred embodiment disclosed,'it should be noted that the relative positions of pivot shafts 122 and 132 and the plunger assemblies 124 of the E and P units, and the relative positions of the bearing balls 130 and 144 and the pivot 142, have all been selected to provide a one-to-one ratio between movementsof the plunger assemblies and the relative gear spindle movements which they control, e.g., for each 0.001 inch movement of the E-unit plunger, the gear spindle moves 0.001 inch along the E axis. In this regard, attention is called to the fact that in order to maintain this desired 1:1 ratio, where the shaft 132 would otherwise interfere with the swivel 128, ball 130, and plunger assembly 124 of the E-motion unit (see FIG. 5), the shaft 132 is slotted to accommodate that assembly.

With reference now to FIG. 6, as the G motion linear actuator plunger 124 is moved axially, the associated bearing ball 130 pivots an arm 140 about the pivot 142, in turn pushing the arm 140 against a ball 144 to move the gear spindle housing 112 longitudinally. The ball 144 is mounted with respect to the pivot bracket 120 by a swivel cup 148 mounted on a slide 150 which permits sliding between the swivel cup 148 and the slide 150 only during E and P movements. A spring 146 biases the pivot bracket 120 to maintain the entire G motion assembly (120, 140, 144, 130 and 124) in firm engagement.

SEQUENCE OF MACHINE OPERATIONS Before explaining the sequence of machine operations in detail, it will first be described here in a general manner:

After a gear and a pinion have been mounted on their respective spindles, the drum 30 for controlling machine functions advances the gear head structure 50 so that the gear member meshes with the pinion. If the pinion and gear teeth are prealigned at the time of loading, the pinion spindle will not be rotating. Otherwise,

automatic meshing is provided by the turning of the pinion spindle 18 at a slow rate (10 rpm). As soon as the teeth mesh, the pinion spindle drive motor is turned off. The gear head structure 50 is then advanced again to bring the gear into metal to metal engagement with the pinion (sensed by a pneumatic switch not shown), and the gear head structure 50 clamps to the cross side 42.

Next, cycle drum 30 enables the lapping motion control circuits of the controller unit 12 (described in greater detail below) to cause machine operations to proceed in the following order as determined by the settings entered into the control panel of controller 12 (the left half of this control panel being shown in detail in FIGS. 8 and 8A and described in detail below:

1. The gear spindle housing 50 then withdraws along the G axis by the distance entered on the lapping motion control panel switch 252 for setting the backlash (Row a at top of FIG. 8).

2. The pinion spindle 18 is accelerated to a predetermined speed for rough lapping and in a direction for lapping the reverse (i.e., coast) side of the teeth. At the start of this acceleration, the gear spindle 20 is moved (set-over") by the mechanism described above to establish a desired mean" tooth-contact position for the rough lapping motions, and the lapping compound pump is turned on (The system for delivering the lapping compound to the gears is not shown, since such systems are old and not essential to an understanding of the subject invention.) After the start of acceleration, the lapping brake (hydraulic motor 32) is activated to provide a preset rough lap" load and the rough lap motions take place. The preset spindle speed and brake load remain in effect throughout the rough lapping event.

3. At the conclusion of this first rough lap" event,

one of the following courses is initiated:

a. No further lapping is done on the reverse side. (Signaled by OFF setting on selector switch 263 at row k FIG. 8.) The controller 12 steps ahead to events involved with lapping the forward (i.e., drive) side of the teeth, and the events described two paragraphs below begin. Or

b. The reverse side of the teeth is finish lapped using the feather" lap sequence. (Signaled by MEAN setting on selector switch 263 at row k.) Or

c. The reverse side is finish lapped in two additional cycles as part of the novel three-cycle lapping sequence described generally above. (Signaled by TIP setting on selector switch 263 at row k.)

4. At the beginning of the finish lap sequence, the

drive motor 24 output shaft speed and the lapping torque supplied by the brake 32 are switched to the values present for finish lapping. Simultaneously, the gear spindle 20 is moved to the Set- Over to Finish Lap (row f) which has been predetermined as the proper mean tooth-contact position for the finish lapping movements. The finish lapping sequence whetherTIP" or MEAN"- is then carried out.

5. Immediately upon completion of the finish lapping sequence for the reverse side, the gear spindle 20 is moved to the desired mean position for the rough lapping of the forward side of the gear teeth. (As will be appreciated by those skilled in the art, just as different mean points are desirable for rough and finish lapping motions on the same side of a tooth, it is desirable to establish still other mean points for the opposite tooth faces.) This last-mentioned spindle movement is selected by setting a Set-Over to Rough for the forward side of the teeth, such a setting being made on row b of the forward half of the control panel which is not shown but is similar to that portion of the panel which is illustrated in FIG. 8. Concurrently with the change in the spindle position, the direction and speed of drive motor 24 is reset for rough lapping the forward side, the lapping brake load being released during the time motor 24 changes directions.

6. When the drive motor is at or near the speed required for rough lapping the forward side, the lapping brake is reset to a load desired for rough lapping the forward side, and the rough lap motions for the forward side can begin.

7. At the conclusion of this rough lap event, any one of the courses indicates at 3 above can be repeated for the forward side of the teeth.

8. Similarly, the finish lap sequences for the forward" side are carried out in the same manner as was described above for the reverse" side in paragraph 4.

9. At the conclusion of the finish lapping sequence for the forward side, a number of events take place simultaneously.

a. The flow of lapping compound is turned off.

b. The electronic relief valve that controls lapping torque is switched to its minimum setting.

c. A signal is sent to the cycle drum to permit it to advance to its next control sequence, withdrawing the gear head structure 50 to its load position.

10. Shortly after initiating the events at step 9 above, a special sequence of motions occurs in the lapping motion system.

a. The data for the last set-over is used to return the step motors 68 to their initial positions. This is done by reversing the sign of the data entry and moving each axis by the distance entered in thumb wheel switches on the control panel.

b. The G axis is then moved forward by the distance entered for setting the backlash.

ll. A signal is transmitted to the cycle drum 30 indicated that the lapping cycle is completed. This permits the cycle drum to move to its position for beginning the complete lapping routine once again for the next gear pair.

LAPPING CYCLE CONTROLLER The sequence of events just described above includes, during each lapping event, the movement of gear spindle 20 through a series of motions calculated to move the point of contact between the gear pair to achieve the'lapping action desired for properly finishing the surface of the teeth and assuring proper tooth contact when assembled. The movement of the gear spindle 20 is controlled by the simultaneous movement of the E, P and G linear actuators in response to control pulses fed to their respective stepping motors, as described above. The generation of such control pulses will now be described with reference to the simplified block diagram of FIG. 7.

That portion of the diagram to the left of the dashed line represents the control circuitry for just one axis motor, for one particular cycle of operation, and it should be understood that two more similar circuits (not shown) are provided for the other motors. The right hand portion of the diagram is common to the control circuit for all three axes, G, P and E. It will also be appreciated that only two switches (202 and 204) related to the direction and displacement along one axis for one particular cycle, are shown in FIG. 7, even though there are similar switches for each cycle (as can be seen from panel board in FIG. 8). Therefore, it will be understood that in actual practice the output of the other switches appearing on the control board, for the other axes and for different cycles and settings, similarly feed into the circuit in the same manner as is shown for the three switches illustrated.

The five top boxes all represent binary-codeddecimal switches which, as is well known in the art, provide a particular binary output for each one of a plurality of predetermined switch settings. For purposes of illustration, it can be assumed that the two switches 204, 206 on the top left correspond to desired movement along the P-axis during part of the particular cycle shown selected on line e of FIG. 8, namely, during a mean-to-heel" cycle which is to last 6 seconds, the cycle to be repeated twice (i.e., two passes" to be made), with a rate of 60 for the selective extra roughing of one portion of the mean-to-heel path.

It will be appreciated that the individual components which comprise this circuit are all well known and understood in the art, many being commercially available items. It is the particular method carried out by the sequential operation of the described circuits, in accordance with a predetermined program of control logic, that has been heretofore unknown.

Since it may facilitate understanding of the moredetailed explanation of this control circuitry which appears hereinbelow, the operation of this circuitry will first be described in a general manner as follows; The

distance and direction of movement along any one axis G, P or E is preselected by setting of the appropriate switches on the control panel. The preselected distance is divided by the time alloted for this displacement (also preselected by switch setting) to determine a displacement rate which is defined in terms of pulses per second to be fed to the stepping motor controlling that particular displacement. The stepping motor is then fed pulses at the desired rate for a period determined by timing circuits, the resulting rate of pulses over the prescribed time producing the desired displacement. It will be appreciated that such displacements are occurring simultaneously on all three axes during the same prescribed time period. After each individual lapping cycle has been completed, that is, a movement to full displacement and return to starting position, the cycle may be repeated as many times as has been selected on the passes switch relating to that particular cycle. During the cycle, when the displacement has reached some preselected point, the cycle may be slowed down (in the illustrative case by 60 percent) to increase accordingly the amount of lapping time'over this particular portion of the tooth surface. This latter feature is accomplished by slowing down the time clock which controls the sequence of events in the apparatus. After each pair is lapped, the displacement mechanism is physically checked (by the zero lock system described below) to assure proper operation and to avoid the possible build-up of errors.

Operation of this circuitry will now be described in more detail. Referring to FIGS. 7 and 8, certain direction, distance, and time information relating to the desired movement along the P axis is preset in respective switches 202, 204 and 206 (Row c in FIG. 8). This information, encoded in binary form, is fed to an arithmetic unit 208 which calculates the rate at which the step motor must be operated to coordinate the desired P-axis displacement with the similar displacements selected for the other axes. This rate is fed to the axis pulse control unit 210 which includes a binary rate multiplier", a well-known electronic component which divides (i.e., multiplies by a fraction) an incoming train of pulses to produce an output pulse rate which varies in accordance with the particular binary numeral fed into its control. In other words, the arithmetic unit 208 produces a binary numeral output which, when fed into the binary rate multiplier of the axis pulse control unit 210 will produce the rate of pulses desired to control the stepping motor. As a check on operation of the arithmetic unit and/or of the lapping program set by the operator, the output of the arithmetic unit is also sent to an excessive rate error detector 212 which provides an error signal 254 in the event that the rate selected is beyond the capacity of the motor.

The information from the time" switch 206 is also sent to a cycle time counter" 214 to preset the number of timing pulses required for it to indicate completion of the cycle. These timing pulses are produced by a timing pulse generator" 216 which is merely a divider which reduces the number of master clock pulses produced by the master clock oscillator 218 and delivered to the circuit through pulse divider"244 This master clock pulse train is the same pulse train which is used as the input to the axis pulse control unit 210 to produce the desired rate of stepping motor pulses asjust described above.

According to the direction originally selected on switch 202, pulses of appropriate polarity and rate are then fed by the axis pulse control unit 210 to the step motor 68 until completion of the timing cycle is indicated by counter 214. System control logic circuits 224 then cause pulse control unit 210 to reverse polarity, and the same number of pulses of opposite polarity are fed to the step motor 68 until counter 214 indicates the return of gear spindle to the same position from which the cycle had been commenced.

It should be understood that the position of gear spindle 20 at the beginning of each cycle is determined by the settings made on the setover" switches of the control panel (rows b and f in H6. 8). Changes in setover positions are made prior to each lapping cycle by the appropriate addition or substraction of the preselected setover displacements from a mean zero" position or from a previous setover position. While FIG. 7 does not include such setover switches, it can be appreciated that they are binary-coded-decimal switches similar to those described above and that the l arithmetic unit 208 and axis pulse control 210 operate 1 in the same manner generally described above, driving the step motor to position spindle 20 along the P-axis at the place selected as the proper mean" position for each lapping cycle.

If the system is operating with ideal accuracy, following the completion of lapping a gear pair, including a plurality of cycles controlled in the manner explained above, the gear head structure is withdrawn to permit unloading of the gears and the pulse counter 228 should return to zero. This corresponds to the datum position of gear spindle 20 when the gear pair is in full mesh without backlash. However, because of inertia, improper mechanical response, etc., the stepping motors may not return to their exact datum (i.e., zero) positions and, as a practical matter, such mechanical sluggishness can generally be expected to result in actual inaccurate movements of as much as three to four ten-thousandths of an inch. The novel apparatus of the subject invention includes a zero-lock mechanism (described in greater detail below) designed to accommodate such expected, practical inaccuracies. At the end of each complete machine cycle, if the stepping motors have not returned exactly to their zero position, they are driven by additional pulses until the zero-lock" mechanism indicates that they have been properly reset. Of course, it is always possible that, due to some mechanical malfunction, a stepping motor and its related linear actuator 66 may not be capable of accurately following the control pulses and that the resulting inaccuracies are beyond permissible tolerances. Such error is detected by the position error" circuit 230 in the event that the number of pulses required, after the end of all lapping cycles for a gear pair, to return the stepping motor to its proper zerolock position is greater than the number of pulses considered necessary to move the motor within normal tolerances. That is, if pulses representative of a mechanical movement greater than three to four tenthousandths of an inch are registered on the counter during zero-lock resetting, a warning signal 231 is provided, since such movement indicates that some mechanical failure is preventing proper machine response to the pulses generated by the lapping control circuits.

It can also be appreciated that the actual mechanisms of the lapper may not respond in any way whatsoever to the control pulses of electronic controller 12. For instance, if a stepping motor does not respond at all to the pulses fed to it, it would remain in its proper zero-lock position and no error would be indicated by position error circuit 230 even though the machine was totally inoperative as to the desired movement along a particular axis. In order to provide a check against such a major malfunction, the system control logic 224 provides an additional no motion check by (l) first causing the withdrawal of the zerolock mechanism, (2) delivering checking pulses to the motor to move it a distance known to be sufficient to prevent proper closing of the zero-lock mechanism, and (3) then operating the zero-lock mechanism. If the zero-lock mechanism indicates that the motor has actually been displaced in response to the checking pulses, then the zero-lock mechanism is once again operated in the manner just generally referred to above to return the step motor to its proper datum position. However, if following the final check displacement the zero-lock mechanism indicates that the stepping motor is still in its zero" position, then it is apparent that the stepping motor is not properly responding to the pulses being delivered to it and an appropriate warning signal 232 is provided by final check circuit 233. This warning is accompanied by appropriate P, G, or E lights 235 to indicate which particular stepping motor has failed to respond to the final motion check.

The position error and final motion checks which have just been described occur only at the end of the total cycles which have been preselected for one gear set. That is, when all cycles are complete and both sides of the gear teeth have been rough and finish lapped, the arithmetic units reverse all of the setover motions to return the lapper mechanism to its zero" position, and it is at this time that the checks just referred to above are made.

It will also be appreciated that each cycle of stepping motor action is repeated as desired in accordance with the information selected on the passes switch 234, the system control logic circuits 224 merely repeating the cycle until the number of cycles indicated have been appropriately counted on cycle counter 236.

In order to provide a greater control over the lapping cycle, the subject lapping apparatus also provides for greater lapping of particular portions of the tooth surface during the roughing cycles. This greater time is achieved in an extremely simple manner, namely, by slowing the clock (which regulates all lapping movements) during that particular portion of the lapping cycle. Assuming that it is desired to spend more lapping time in one particular area near the heel of the tooth during the rough lapping cycle, the operator first selects that portion of the overall cycle during which lapping is occurring between the mean setover position and the heel, by setting position switch 238 (row e of FIG. 8) to H. He then selects the particular position at which this extra lapping is to occur by determining how long after the cycle is initiated that the desired slowdown should begin. For instance, assuming that a mean-to-heel basic cycle time of 6 seconds has been set initially (on time switch 206 at row c in FIG. 8 and that it is desired to obtain longer lapping over the outer portion of the heel, the operator sets time switch 240 (row e of FIG. 8) to 3 which will result in the desired slow-down occurring after the first three seconds of the 6-second cycle. (The position and time selector switches are not shown in FIG. 7.) To provide the amount of extra lapping desired this particular tooth area, the operator next sets percent rate" switch 242 to a value indicating the amount by which the normal speed of the lapping motion is to be slowed during this portion of the cycle, for instance, to 60 percent of the normal rate. Such slow down increases the amount of time the gear pair run together making contact at this portion of their teeth, thereby increasing the amount of metal removed by the lapping process.

At the desired time, system control logic 224 open gate 243 and the binary information encoded on switch 242 (representing in this example the 60 percent rate passes through to the pulse divider 244 which is simply another binary rate multiplier positioned between the master clock oscillator and the remainder of the circuit. This binary input causes the pulse divider to divide the pulse rate of the master clock oscillator, thereby slowing down all three lapping movements to the 60 percent rate. As soon as the cycle time counter 214 has counted the number of pulses indicating the cycle point at which all of the stepping motors are to be reversed to return to the mean position for the cycle, the gate 243 to the percent rate switch 242 is closed and the output of the pulse divider returns to the normal pulse rate for the remainder of the cycle.

It will be appreciated that no attempt is being made to describe the many logic circuits, including reset pulses which clear the various counters, binary rate multipliers, arithmetic units, etc., since these are matters which are well known in the art and, given the general sequence of operations described above, can be easily reproduced by persons skilled in electronic controls.

THE CONTROL PANEL In FIG. 8 there is shown an arrangment of that portion of the switch panel of control unit 12 relating to the lapping of the reverse (coast") side of the teeth. The panel 250 contains an array of thumb-wheel switches for entering the data which controls the selected lapping cycle sequence and the distances, directions and rates of the 3-axis movements effected by the stepping motors. It should be understood that control unit 12 includes a second panel similar to panel 250, but operative to control lapping cycles for the forward (drive") side of the teeth of the gear pair being lapped.

Settings for Tip Lapping Method The control panel settings for a typical lapping sequence employing the novel peripheral (tip) lapping method of the invention will now be described, with reference being made to FIG. 8 and to the method steps set out above under the heading SEQUENCE OF MACHINE OPERATIONS.

At the top of FIG. 8 in row a are switches 252 and 253 for setting the initial backlash in terms of G-axis displacement away from metal-to-metal engagement.

The backlash setting, like the other axial displacements for set-overs and lapping motions, is accomplished by the same electronic logic circuits described above, being calculated at a rate of some number of control pulses per second for the time period alloted to the displacement. In the case of initial backlash setting, switch 252 provides the arithmetic unit with the displacement desired, while T switch 253 sets the alloted time which must be sufficiently long to assure that the displacement can be made without exceeding the maximum pulse response time of the G-axis stepping motor, or else the Excessive Rate" warning light 254 will be lighted at the bottom of the panel (see also FIG. 7). After backlash is set, the gear set is in proper position for running together, and this may be done at low speeds in both directions to test for nicks and burrs. However, such testing is not part of the subject invention and for purposes of this disclosure the proper running position merely establishes the zero position for all axis displacements made thereafter.

On the left hand portion of control panel 250 in FIGS. 8 and 8A, are superimposed small representations of gear teeth each of which is intended to illustrate schematically the tooth contact pattern effected by the settings of the thumbwheel switches shown on each of the respective rows, a through k, of the panel. It

. is assumed that the particular gear pair being lapped when in proper running position with the backlash set as just described above, has an initial tooth contact pattern shown by the dotted lines on the gear tooth in row a, the mean point of this contact pattern being designated by the point 256. In lapping this particular gear pair, it is desired to improve its initial tooth contact pattern by moving it to a more central location on the tooth and by narrowing it according to the novel method described herein, thereby to improve the adjustability and noise characteristics of the gear pair in assembly. The remaining settings on control panel 250 are selected to provide rough and finish lapping cycles which will result in the desired improvement of tooth contact.

At the start of rough lapping, spindle 20 is setover along its E, P, and G axes by the amounts indicated on the switches in row b. This set-over effectively changes the mean point of tooth contact from 256 to 258, establishing the starting point for the tooth contact traverses which are used during the rough lapping cycle. It should be noted that this set-over also includes a time switch necessary to make this desired displacement compatible with the pulse rate system used to control the stepping motors.

The switches in rows c and d describe the end points, toward the heel and toe of the tooth, respectively, to and from which the tooth contact point will be traversed during the rough lapping cycle. It can be seen that these settings will result in a greater traverse over a longer period of time toward the heel, a shorter traverse of less duration being made to and from the toe portion of the tooth.

The logic circuits referred to above are programmed to cause one traverse to be made to the heel followed by one to the toe, this complete movement being considered one lapping pass. Switch 234 determines how many such passes will be made during the rough lapping cycle, while pinion spindle speed and brake load are determined by the settings of switches 260 and 262. In addition, Selective Rough Control switches 238, 240 and 242 provide for extra lapping of the heel portion of the gear teeth, as was explained above under the heading LAPPING CYCLE CONTROLLER.

As the result of the rough lapping cycle, it is assumed that, when in proper running position, the tooth contact pattern will have been changed to that indicated in dotted lines on the gear tooth superimposed on row e, with mean point 256 being moved to the center of the tooth.

As explained above, the apparatus disclosed herein provides either one of two finishing cycles, tip or feather". The respective settings for set-over and traverses for each of this finishing operation, and the respective effects of these settings are shown, respectively, at the bottom portion of FIG. 8 and in FIG. 8A.

To carry out the novel tip lapping method of the invention herein, it is necessary to use two distinctly different set-overs during the finish lapping cycles, on (shown in row j) moving the mean position of toot contact to a point 259 near the tip (high on the addendum) of the gear, the other (now h) moving it to the point 261 relatively low on dedendum of the tootli. (Note: Point 261 coincides with a point near the tip of the mating gear being lapped.) The row g andj settings, for establishing the end points of the traverse of the tooth contact during each of the two tip lapping cycles, are given in the direction of the heel only. However, when Finish Operation switch 263 is set to TIP, the logic circuits automatically calculate the reverse of these settings to determine the toe portion of each of the two finishing cycles, and therefore the actual contact point moves along the tip periphery of the gear teeth toward both heel and toe during each complete pass, as schematically shown in the superimposed gear? tooth representations. During these finishing cycles, pinion spindle speed and brake load are controlled by the settings of switches 264 and 266. i

As a result of the tip lapping finishing cycles, the running position tooth contact pattern is narrowed (as shown in dotted lines on the gear tooth on row k of FIG. 8) in the manner contemplated by the novel method described hereinabove. This lapping method has been shown to improve the adjustability of gear pairs in assembly by more than 200-300 percent, thereby providing industry with great savings from reductions in initial assembly time, reassembly of rejects, and concommitant labor costs.

Following completion of the reverse side lapping cycles just described, the foreword side of the teeth are lapped in a similar manner. However, it should be understood that while the controls (not shown) duplicate those for reverse lapping, totally different displacements, traverse rates, rotation rates, brake torques and even a different method may be selected, if desired.

Settings for Feather Lap" Finishing Cycle FIG. 8A shows the lower portion of control panel 250 with the switches in rowsfthrough k being set to provide the alternative mean or feather" lap finishing cycle. In this operation, the selection of MEAN on switch 263 automatically by-passes the second setover switches of row h, and rows g and j are used to control respectively the heel and toe traverse, giving the same independent control (referred to in the art as split-bias" control) for this finishing cycle as is available in roughing as explained above.

The new mean position 268 for the feather lapping finishing cycle is substantially coincident with the mean point of the tooth bearing which will be used when the gear pair is in proper running position, namely, near the center of the new tooth bearing area (row e) produced by the semi-finish lapping cycle.

The effect of the feather lap finish is to provide an extremely refined tooth surface without appreciably disturbing the tooth contact pattern established during the rough lap cycle (as shown by schematic representations at row e of FIG. 8 and row k of FIG. 8A).

It is emphasized that the particular data entered on the control panel of FIGS. 8 and 8A and used in the above related discussion are merely exemplary of the exceptional versatility of the subject novel apparatus, and that no attempt has been made herein to exhaustively catalog the many different combinations of settings and steps which will be understood by those skilled in the art to be possible with the subject apparatus.

ZERO-LOCK MECHANISM As explained above, because of missed control pulses, sticky linkages, or other machine malfunction, the stepping motors may not return exactly to their pre-calculated zero" positions following completion of the lapping of a gear pair, and to check for such malfunction and to ensure that the machine elements are in proper position for lapping the next gear set, a zerolock mechanism is provided.

Referring once again to FIGS. 3 and 4, each linear actuator unit 72 includes a dog 96 shown secured on the sleeve 78 to rotate with the sleeve 78 and the nut 82. The dog is shaped to have two angularly separated, oppositely outwardly facing side surfaces 98 disposed a predetermined distance apart. There is further provided two pistons 100 slidably mounted in one side of the housing to project laterally into the housing. The pistons have side surfaces 102 which face one another and which are so close that when the dog 96 is generally directed toward the pistons, the pistons can only slide inwardly along the side surfaces 98 of the dog if the dog is precisely oriented at a predetermined angular orientation on the linear screw. Thus, since the dog is fixed with respect to the sleeve 78 and the nut 82, the pistons can extend only when the linear screw has a precise, predetermined axial location.

The pistons 100, which are biased by springs 105 toward interference with or sliding capture of the dog 96, are also selectively retractable out of engagement with dog 96 in response to fluid pressure in chamber 104. The pistons 100 carry axial tail pieces to which limit switch trips 106 are secured for actuating limit switches 108 in dependence upon the axial disposition of the pistons 100. Upon retraction of the pistons 100, the dog trips 106 actuate the switches 108 to a first position, and upon return of the pistons to a dog-capturing extension as depicted in FIG. 4, the trips 106 actuate the switches 108 to a second position. So long as the pistons are retracted, the dog 96, sleeve 78, and nut 82 are free to rotate and axially extend and retract the linear screw 84. A release of fluid pressure in the chambers 104 allows the pistons to be forced toward their FIG. 4 positions by the springs 105.

As was described above, at the end of a complete lapping routine, the system control logic reverses all of the various set-overs made for the different lapping cycles, including the original backlash setting, thereby theoretically returning all of the mechanism for controlling the 3-axis movements of the gear spindle to its original zero position. If, at this time, both pistons 100 of each linear actuator unit 72 are not in their fully extended position, i.e., if either limit switch 108 is still in its first position, pulses of appropriate polarity are delivered to the respective stepping motor to rotate dog 96 in the direction of the piston which has already moved to its extended position as indicated by its respective switch 108. Under normal circumstances, only a few pulses should be required before dog 96 returns to its zero position permitting the second piston to also extend, indicating that proper zero-lock has been achieved. However, if an excessive number of pulses are required to return the stepping motor to its proper zero position (e.g., indicating final position error in excess of 0.0007 inches), such position error is indicated by final motion warning light 231 (see FIGS. 7 and 8) as explained above.

As was also explained earlier, a final check is made by retracting the pistons 100, driving each stepping motor and its related dog 96 to a predetermined pistonblock position, and releasing the pistons 100 to their extended positions. if the switches 108 for any of the actuator units indicates that both pistons have returned to their extended positions, it is apparent thattheir related stepping motor is not properly responding to the control pulses, and this condition is indicated by NO MOTION" light 232 (see FIGS. 7 and 8).

SUMMARY The novel vertical pinion spindle/horizontal gear spindle configuration of the lapping apparatus disclosed herein uses less floor space, permits the operator to get closer to the workpieces, and facilitates use of automatic loading mechanisms.

The exceptionally versatile control arrangements of the subject apparatus can provide: (1) conventional rough lapping to produce a good surface finish over the entire tooth surface, correct the location of the bearing on the tooth, and control bearing length; or (2) rough lapping followed by mean or feather lapping to obtain the above plus optimum surface finish in the central area of the tooth, thereby minimizing objectionable sound characteristics due to finish; or (3) rough lapping followed bya novel peripheral lapping or tip lapping to achieve the controls of the rough lap plus the described advantage of relieving the tops and deep flanks.

The novel peripheral lapping method can provide mating tooth surfaces which have substantial mismatch (or ease-of both lengthwise and profilewise, and thus a full perimeter of no contact can be produced or preserved in lapping, thereby remarkably improving tolerances for adjusting the gear pair in assembly while maintaining desirable low-noise characteristics.

It should be evident that the machine and method disclosed permit immeasurably greater freedom of control over the lapping of gear pairs than has heretofore been available and permit the manufacture of lapped gear pairs having remarkably improved characteristics.

It should also be apparent that the gear lapper and method as described hereinabove can be modified and adapted to the needs of practice without departing from the spirit and scope of the principles of the invention as outlined and explained in this specification.

What is claimed is:

1. In a method for lapping a pair of gears by running together in mesh wherein said gears are relatively oriented to a first mean position and then said relative orientation is progressively altered to traverse the tooth bearing generally lengthwise 'of the teeth for refining the surface of said teeth, the improvement comprising the further steps of:

setting over the relative orientation of said gears to a second mean position displacing the tooth bearing to a position near the tooth tips of one of said gears;

progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth;

setting over the relative orientation of said gears to a third mean position displacing the tooth bearing to a position near the tooth tips of the other of said gear pair; and

progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth. 2. The method of claim 1 wherein at least one of said lengthwise traverses moves said tooth bearing along first preselected path from the mean position first toward one end of the teeth and back to said mean position, and then along a second preselected path toward the opposite end of the teeth and back to said mean position.

3. The method of claim 2 wherein, during a portion of the traverse along at least one of said preselected paths, the rate of said traversal is slowed down to increase lapping time in that area of the gear teeth.

4. The method of claim 1 further comprising reversing the direction of rotation of said gear pair and repeating said steps for the reverse sides of the gear teeth.

5. The method of claim 4 wherein at least one of said mean position orientations for the reverse sides of the teeth differs from the corresponding mean position used when lapping the forward sides of the teeth.

6. The method of claim 1 wherein all of said relative orientations are produced by moving only one gear of the pair being run together.

7. A method for lapping a pair of gears by running together in mesh comprising the steps of:

relatively orienting said gears to a mean position wherein the tooth bearing is near the tooth tips of one of said gears;

progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth;

setting over the relative orientation of said gears to a further mean position displacing the tooth bearing to a position near the tooth tips of the other of said gear pair;

progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth.

8. The method of claim 1 wherein, during a portion of the traverse along at least one of said preselected paths, the rate of traversal is slowed down to increase lapping time in that area of the tooth. 

1. In a method for lapping a pair of gears by running together in mesh wherein said gears are relatively oriented to a first mean position and then said relative orientation is progressively altered to traverse the tooth bearing generally lengthwise of the teeth for refining the surface of said teeth, the improvement comprising the further steps of: setting over the relative orientation of said gears to a second mean position displacing the tooth bearing to a position near the tooth tips of one of said gears; progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth; setting over the relative orientation of said gears to a third mean position displacing the tooth bearing to a position near the tooth tips of the other of said gear pair; and progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth.
 2. The method of claim 1 wherein at least one of said lengthwise traverses moves said tooth bearing along first preselected path from the mean position first toward one end of the teeth and back to said mean position, and then along a second preselected path toward the opposite end of the teeth and back to said mean position.
 3. The method of claim 2 wherein, during a portion of the traverse along at least one of said preselected paths, the rate of said traversal is slowed down to increase lapping time in that area of the gear teeth.
 4. The method of claim 1 further comprising reversing the direction of rotation of said gear pair and repeating said steps for the reverse sides of the gear teeth.
 5. The method of claim 4 wherein at least one of said mean position orientations for the reverse sides of the teeth differs from the corresponding mean position used when lapping the forward sides of the teeth.
 6. The method of claim 1 wherein all of said relative orientations are produced by moving only one gear of the pair being run together.
 7. A method for lapping a pair of gears by running together in mesh comprising the steps of: relatively orienting said gears to a mean position wherein the tooth bearing is near the tooth tips of one of said gears; progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth; setting over the relative orientation of said gears to a further mean position displacing the tooth bearing to a position near the tooth tips of the other of said gear pair; progressively altering said relative orientation to traverse the tooth bearing generally lengthwise of the teeth.
 8. The method of claim 1 wherein, during a portion of the traverse along at least one of said preselected paths, the rate of traversal is slowed down to increase lapping time in that area of the tooth. 